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Spinal CSF Spaces
The spinal cord (and brain) are protected by three layers of tissue, called spinal meninges, that surround the canal. These are all continuous with the cerebral meninges at the level of the foramen magnum. The spinal epidural (extradural) space is located between the spinal dura mater and the vertebral column and extends from the foramen magnum to the sacral canal at the level of S2/3. Boundaries * Inner: spinal dura mater * Outer: posterior longitudinal ligament, neural arches/intervertebral foramen, ligamentum flavum, periosteum of the vertebral bodies, pedicles and laminae Contents * loose areolar connective tissue: occupy in the posterior part of the epidural space and extend laterally into the intervertebral foramina with the nerve roots and their dural sheath. * semi-liquid fat * internal vertebral venous plexus: occupy the anterior and partly posterior aspect of canal as longitudinal aligned venous network with transverse communication. Basivertebral veins drain into the plexus at each vertebrate level. * lymphatics * arteries * spinal nerve roots The dura mater is the outermost layer forming a tubular sheath of dense inelastic fibre. It extends downwards to the level of the S2 vertebra. Attachments: * Tectorial membrane * Periosteum of the upper cervical vertebra and their ligaments * Posterior longitudinal ligament The spinal dura is pierced by the anterior and posterior roots of the spinal nerves and the dura wraps around them like a sleeve and fuses with the epineurium of the mixed spinal nerves distal to the dorsal root ganglion. The arachnoid mater is the middle delicate layer that lines the dura. It invests the spinal cord loosely. It descends to about the S2 vertebral level and covers the cauda equina extensively. The subarachnoid space between the arachnoid and pia accommodate about half the of the total volume of the CSF. It communicates through the foramen magnum with the subarachnoid space of the posterior cranial fossa. The space ends at level S2. * Lumbar cistern. It extends from the conus medullaris (L1-L2) to S2. It contains the filum terminale and the nerve roots of the cauda equina. It is from the cistern that CSF is withdrawn during lumbar puncture. * Content: CSF, vessels, spinal cord ligaments, nerves, filum terminale The pia mater is the innermost layers. It invests the surface of the spinal cord and sulcus, blood vessels. The cord is stabilized within the dura mater by the connecting denticulate ligaments. Extensions: * over the spinal roots until the dura fuses with the epineurium * below the conus medullaris, and extends as the filum terminale which perforate the spinal theca at the level of S2 and descend on the back of the coccyx. * lateral expansions of the pia mater forms the denticulate ligament. This flange crosses the subarachnoid space between the anterior and posterior nerve roots and piercing the arachnoid and connects the side of the spinal cord to the dura mater. There is around 21 pairs of denticulate ligaments on each side. Each help to anchor the spinal cord and prevent side to side movement, providing stability. Arterial supply * Radicular arteries segmentally Venous drainage * Segmental drainage via the vertebral venous plexus into the azygos system Nerve supply: * recurrent branches of the spinal nerves entering the intervertebral foramina